This is all historical revisionism. You need to look at the reasons that were given at the time, not the reasons people made up to justify and obfuscate what they did decades later.
You could be forgiven for thinking this was just historical revisionism if you only looked at superficial news weeklies and ignored all foreign policy forums from the late 90s and early 2000s.
EDIT: Oh, I forgot Saddam's attempted assassination of a sitting US President, which Bush cited in a campaign speech as a reason he needed to be toppled: http://historynewsnetwork.org/article/1000
Most of these complaints with Saddam were aired at the time, in various forums. Some may have gotten more airtime, because they were more directly involved with UN processes or more sensationalist for journalists, but that doesn't mean the others weren't causes of the war. If you wanted one sole cause of the war it would have been ten years of defying sanctions and bellicose rhetoric after the 1991 Gulf War. Any read of primary sources from the late 90s about US-Iraqi relations makes that much more clear.